The objectives of this proposal are to: 1) revive a highly successful international forum of scientists for the exchange of ideas and the discussion of unsolved issues on the role of vestibular organs in the exploration of space; 2) foster productive interchange of ideas between established investigators, students and young investigators; and, 3) produce a document that specifically addresses vestibular physiological changes resulting from sustained microgravity and how these changes interact with other biological systems. Resulting publications will clearly address what is known, what is not known, what must be done and what resources will be needed to investigate the unknowns. This symposium will follow the pre-Barany 2002 (Orcas Island) meeting on "...the influence of vestibular signals on the control and perception of movement...," and the 2002 Extraordinary Barany meeting (Seattle) that will focus on "...convergence of basic and clinical perspectives...". This third meeting (Portland, October 1-3, 2002) will focus on the study of vestibular mechanisms in a unique (microgravity) laboratory environment. The meeting format is designed to promote a rigorous discussion of unresolved questions, identify important deficits in our knowledge arising from recent investigations and explore long duration research opportunities on the new International Space Station. Emphasis will be on the unique advantages of the microgravity environment for vestibular research and special problems facing space investigators. The Sixth Symposium on the Role of the Vestibular System in the Exploration of Space will address questions that must be answered in order to support the successful human exploration of space. Manned expeditions to Mars and beyond cannot be accomplished safely until the vestibular physiology of microgravity has been fully defined and effective countermeasures developed to ameliorate the severe consequences of prolonged microgravity exposure. If the goals of this meeting are successfully accomplished one could reasonably expect the resolution of key unsolved vestibular physiological problems that limit the human exploration of space within the foreseeable future.